Apparatus and method for filling carbon dioxide cylinders

ABSTRACT

A device for filling a high-pressure CO 2  cylinder with liquid CO 2  while venting gaseous CO 2  comprises a two-compartment chamber that is installed in the top opening of the cylinder. A first dip tube connected to one compartment extends to the bottom portion of the cylinder and a second dip tube connected to the other compartment extends to the upper portion of the cylinder. Each compartment has a port for flow into or out of the compartment. Liquid CO 2  introduced into the compartment with the first dip tube will flow into the cylinder and cause gaseous CO 2  to exit through the second dip tube and the other compartment. When liquid CO 2  appears in the exiting stream, the introduction of liquid CO 2  is stopped. In a common embodiment, a conventional CO 2  valve has the first dip tube connected to the bottom thereof. A street tee with one end connected to the second dip tube is screwed into the top opening of the cylinder. The CO 2  valve is screwed into the other end of the tee, the first dip tube extending with annular clearance through the second dip tube into the cylinder.

BACKGROUND OF THE INVENTION

This invention relates to an apparatus and method of filling carbondioxide (CO₂) cylinders. More particularly, the invention involvesfilling liquefied CO₂ high pressure cylinders by passing liquefied CO₂from a low pressure container of liquefied CO₂.

High pressure cylinders for liquefied CO₂ have a single valved port and,by long established practice, are filled at a recharging depot whereliquefied CO₂ is pumped into each cylinder through its valved port.Filling is continued until the weight of CO₂ is equal to two-thirds ofthe weight of water that would fill the cylinder. This customary fillinglimit serves to provide a safe vapor space above the liquefied CO₂ inthe cylinder.

In contrast to the common, laborious and costly practice of transportingeach cylinder from a CO₂ user to a depot, filling it while carefullyweighing the added CO₂ to avoid overfilling, and transporting therecharged cylinder back to the CO₂ user, the invention provides a systemof supplying CO₂ to cylinders much like the familiar delivery of fueloil to the tanks at several homes. In spite of the extensivedistribution of CO₂ cylinders and the frequent need to transport each toa refilling depot and back again to the user, no practical proposal isknown for obviating this cumbersome and expensive system of shuttlingcylinders between CO₂ customers and a recharging depot.

Accordingly, a principal object of the invention is to provide anapparatus and method for filling cylinders at various locations withliquefied CO₂ from a large container that is transported to the variouslocations.

Another important object is to provide an apparatus for filling CO₂cylinders which is simple to install and to use.

A further object is provide apparatus that automatically limits fillingcylinders with liquid CO₂ to a selected safe level.

These and other features and advantages of the invention will beapparent from the description which follows.

SUMMARY OF THE INVENTION

In accordance with this invention, three basic elements have been addedto the conventional CO₂ valve that is screwed into the threaded port atthe top of a high-pressure cylinder for liquefied CO₂, namely, a streettee and two dip tubes. A first dip tube, usually a copper tube, issoldered or otherwise connected to the bottom opening in theconventional CO₂ valve. A second dip tube, larger in diameter than thatof the first dip tube, usually a copper tube, is soldered of otherwiseconnected to the end of the tee that has a male thread matching thefemale threaded opening of the cylinder.

The CO₂ valve with the first dip tube is inserted into the opposite endof the street tie which has a female thread. The first dip tube extendsthrough the second dip tube with an annular clearance between them. Whenthe CO₂ valve is fully screwed into the top female end of the tee, andthe bottom male end of the tee is fully screwed into the threadedopening of the cylinder, the bottom end of the first dip tube will beclose to, preferably only about 1 inch above, the bottom of thecylinder. By contrast, the second dip tube will extend down only aboutone-third of the internal length of the cylinder. Thus, liquid CO₂introduced through the conventional CO₂ valve flows down the 30 firstdip tube into the bottom of the cylinder while gaseous CO₂ passes up thesecond dip tube and out of the tee through its side opening which may beprovided with a valve.

The level of liquid CO₂ in the cylinder will keep rising during thefilling operation until it reaches the bottom end of the second diptube. Up to that point, gaseous CO₂ has been leaving the cylinder byflowing up the second dip tube through the annular space between it andthe first dip tube and into the street tee from which it exits at theside opening of the tee.

As soon as the level of liquid CO₂ reaches the bottom end of the seconddip tube, the gaseous CO₂ in the cylinder above the liquid developssufficient pressure to cause liquid CO₂ to flow up the second dip tubeand out of the tee through its side opening. The escaping liquid CO₂flashes into CO₂ snow which 10 signals that the desired liquid CO₂capacity of the cylinder has been reached and the further supply ofliquid CO₂ to the cylinder should be terminated.

Thereupon, the conventional CO₂ valve is closed to stop the flow ofliquid CO₂ into the cylinder and a valve at the side opening of thestreet tee is also closed to stop the escape of gaseous CO₂ from thecylinder. Then the valve connected to the side of the tee has itsdischarge end connected to tubing that can convey gaseous CO₂ to adesired use station, such as a beer dispenser or a soda fountain, andthe valve is opened to permit gaseous CO₂ flow to the use station.

It is noteworthy that the invention involves the simple assembly ofthree common plumbing elements with the conventional CO₂ valve. Two ofthe three added elements are merely lengths of metal tubing, furtherhighlighting the simplicity and low cost of the apparatus of theinvention that eliminates the continuous, cumbersome and expensivetransportation of cylinders between CO₂ use sites and CO₂ supply depots.

However, it should be noted that the composite of the CO₂ valve andstreet tee provides in effect a metal chamber with two 30 compartments:a liquid CO₂ feed compartment in the CO₂ valve above a CO₂ vapor exitcompartment in the tee. Therefore, stated more generally, the inventioninvolves a metal chamber that can be screwed into the top opening of aCO₂ cylinder, the metal chamber having a wall therein to provide twocompartments. Each compartment has a port to the exterior of the chamberand each has a dip tube connected thereto and extending into the CO₂cylinder, the two tubes having different lengths. However, in its basicform, the invention comprises means for sealing the top opening of a CO₂cylinder and for holding two dip tubes extending therethrough into thecylinder to different levels therein.

BRIEF DESCRIPTION OF THE DRAWINGS

To facilitate the further description and understanding of theinvention, reference will be made to the accompanying drawings of which:

FIG. 1 is a schematic representation of a conventional CO₂ valve andthree basic plumbing elements that can be assembled to form theapparatus of this invention;

FIG. 2 is a similar illustration of the items of FIG.1 when assembledand installed on a high-pressure CO₂ cylinder;

FIG. 3 is a cross-sectional view of a specially designed apparatus thatmay be used in lieu of that shown in FIG.1; and

FIG. 4 is a front view of the apparatus of the invention in its simplestand basic embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS

The components of the apparatus of the invention in its common form areshown disassembled in FIG. 1. A standard CO₂ cylinder valve 10 is shownwith a single addition thereto of a first dip tube 11 attached to thecentral opening 12 at the bottom of valve 10 which has the usual valvestem 13 and knob 14 at the top thereof. The bottom end of valve 10 has amale thread 15 matching the female thread of the sole opening at the topof the CO₂ cylinder in which valve 10 was screwed prior to thisinvention. Valve 10 has a threaded port 16 for the flow of CO₂ and alateral cell 17 containing a safety disk that will rupture and releasethe pressure in the CO₂ cylinder if the pressure exceeds a predeterminedsafe maximum.

The other basic components are a street tee 18 and a second dip tube 19connected to the opening at the end of tee 18 which has male thread 20chosen to match the female thread of the top opening of the CO₂ cylinderinto which tee 18 will be screwed. The top end 21 of street tee 18 has afemale thread matching the male thread 15 of CO₂ valve 10 so that valve10 and tee 18 can be screwed together.

Tube 11 connected to CO₂ valve 10 is longer and smaller in diameter thantube 19 connected to street tee 18. In order to screw valve 10 and tee18 together, the first dip tube 11 is inserted in top end 21 and throughtee 18 and second dip tube 19 until the bottom of valve 10 is againstthe top end 21 of tee 18. Valve 10 and tee 18 are then screwed togetherand are ready to be installed in a CO₂ cylinder by inserting theconcentric first and second dip tubes 11,19 through the top opening inthe CO₂ cylinder until tee 18 reaches the female threaded opening at thetop of the CO₂ cylinder. Male threaded end 20 of tee 18 is then screwedinto the top of the CO₂ cylinder to complete the installation of theapparatus of the invention. The lateral port 22 of street tee 18 servesas the discharge opening for the withdrawal of gaseous CO₂ from thecylinder as will be explained in the description of FIG. 2.

FIG. 2 is a diagrammatic representation of the apparatus of theinvention as installed in a high-pressure CO₂ cylinder together withtypical accessories used with the cylinder. The components of FIG. 1,when assembled as the apparatus of the invention, are shown installed ina CO₂ cylinder 23.

First dip tube 11 extends from the bottom of CO₂ valve 10 to close to,say 1 to 2 inches from, the bottom of cylinder 23. Second dip tube 19surrounding tube 11 extends from the bottom of tee 18 about one-thirddown the inside length of cylinder 23. More precisely, the length ofsecond tube 19 is determined by a long established regulation forhigh-pressure CO₂ cylinders. That regulation specifies that the maximumquantity of liquefied CO₂ in a cylinder shall not exceed two-thirds ofthe weight of water that will fill the cylinder. This formula ensures asafe vapor zone in the cylinder above the liquid CO₂ therein. Too smalla vapor zone is dangerous because a very high pressure could develop inthe cylinder to the point of exploding it.

To introduce liquid CO₂ into cylinder 23, the apparatus of the inventionmakes it possible for liquid CO₂ to flow from a supply container intoCO₂ valve 10 through port 16. The liquefied CO₂ flows down valve 10 andfirst dip tube 11, discharging into the bottom of cylinder 23. GaseousCO₂ evolved from the liquid rises in cylinder 23 and flows up second diptube 19 into tee 18 exiting therefrom through lateral port 22. When theliquid level in cylinder 23 reaches the bottom end of second tube 19,CO₂ vapor in the top of cylinder 23 is trapped. If additional liquid CO₂is introduced into cylinder 23, liquid will rise in second tube 19 andflash out of port 22 into dry ice snow. The snow is a visual notice thatthe cylinder has been filled with the allowable maximum quantity ofliquid CO₂ and that the flow of liquid CO₂ into cylinder 23 should bestopped.

To facilitate the introduction of liquid CO₂ and the withdrawal ofgaseous CO₂, high-pressure cylinder 23 is connected to knownaccessories. A manifold 24 equipped with pressure gauge 25 and pressurerelief valve 26 is connected by tube 27 to port 16 of CO₂ valve 10. Inaccordance with this invention, manifold 24 is connected by tube 28 toliquid check valve 29 which is connected to supply tube 30. A quickcoupler 31 is attached to tube 30 to facilitate the connection of a hoseextending from a low-pressure (usually about 300 pounds per square inch)container of liquid CO₂ on a truck driven to the building containing thebar or soda fountain where the CO₂ cylinder requires replenishment ofliquid CO₂. It should be noted that, in the arrangement shown, valvestem 13 with knob 14 has been turned to the open setting and there neveris a need to close it because check valve 29 automatically preventsback-flow through CO₂ valve 10. It is well to note that in theconventional use of CO₂ valve 10 port 16 serves only for the withdrawalof gaseous CO₂ from a high-pressure cylinder. Pursuant to the invention,port 16 is used to introduce liquid CO₂ into a cylinder.

Manifold 32 equipped with pressure relief valve 33 is connected by tube34 to lateral port 22 of tee 18. Manifold 32 is connected by tube 35 toball valve 36 which is connected by tube 37 to muffler 38. Tube 39equipped with pressure regulator 40 and connected to manifold 32 servesto convey gaseous CO₂ from cylinder 23 to a desired use site such as asoda fountain. Manifold 32 may have several ports so that additionaltubes like tube 39 can convey gaseous CO₂ to different use sites.

When cylinder 23 requires replenishment of liquid CO₂, a truck carryinga low-pressure container filled with liquid CO₂ will park near thebuilding in which the cylinder is housed and a hose connected to theliquid CO₂ container will be drawn to connect it to quick coupler 31.The high pressure, say 700 pounds per square inch, in cylinder 23 isreduced by opening valve 36 until the pressure drops to a pressure about15 pounds below the pressure in the supply container. As soon as thepressure in the cylinder drops below that in the supply container,liquid CO₂ flows from the hose through components 30,29,28,24,27,16,10and 11 into the bottom of cylinder 23. Simultaneously, CO₂ vapor evolvedfrom the liquid in cylinder 23 rises and flows up the annular spacebetween first and second dip tubes 11,19 and through components18,22,34,32,35,36,37 and 38 where the CO₂ vapor is vented to theatmosphere. When the level of liquid CO₂ reaches the bottom of seconddip tube 19, gaseous CO₂ can no longer flow into tube 19 and thepressure of gaseous CO₂ trapped in the top of cylinder 23 builds up sothat liquid CO₂ begins to rise in dip tube 19 and flow throughcomponents 18,22,34,32,35,36,37, exhausting from muffler 38 in the formof dry ice. The appearance of dry ice at muffler 38 is the visual signthat cylinder 23 has been filled with the allowable maximum quantity ofliquid CO₂. Thereupon, the hose is disconnected from quick coupler 31and valve 36 is closed. The accessories shown in FIG. 2 make it possibleto draw gaseous CO₂ from cylinder 23 through tube 39 at any timeincluding while liquid CO₂ is being introduced into cylinder 23. This isan additional benefit of the invention; heretofore, the flow of gaseousCO₂ to a soda fountain or other use site was interrupted while adepleted cylinder was being replaced with a freshly charged cylinder.

FIG. 2 shows a single cylinder 23 connected by tubes 27,34 to manifolds24,32, respectively. However, several cylinders can be connected bysimilar tubes to both manifolds 24,32; multiple cylinders are desirablefor large users of gaseous CO₂. It has already been pointed out thatmanifold 32 can have several tubes 39 to convey gaseous CO₂ to differentuse stations. Hence, manifolds 24,32, make it possible to supply liquidCO₂ simultaneously to several cylinders 23 connected in parallel theretoas well as permit the flow of gaseous CO₂ to several use stationswithout any interruption.

The simplicity of the invention is enhanced by the fact that all of thecomponents are common plumbing parts. For example, both dip tubes 11,19and all the tubes connected to manifolds 24,32 can be copper tubing.Optional muffler 38 is used to deaden the sound of escaping CO₂ duringthe filling of cylinder 23 with liquid CO₂. While the flow of liquid CO₂from the low-pressure container on the truck to a cylinder requiringreplenishment can take place merely because the pressure in the supplycontainer is higher than that in the cylinder, a pump mounted on thetruck may be used to hasten this filling operation.

Even though the apparatus shown in FIG. 1 is formed of readily availablecomponents that are not expensive, the functions of that apparatus,namely, the simultaneous introduction of liquid CO₂ into, and venting ofCO₂ vapor from, a cylinder can be achieved with a specially designedapparatus. FIG. 3 is a cross-sectional view of one such apparatus. Acylindrical metal chamber 45 has a male thread 46 at one end 47 whichmatches the female thread of the sole top opening of the CO₂ cylinderinto which chamber 45 will be screwed. A wall 48 extends from end 47 tothe opposite end 49, dividing chamber 45 into two compartments orsections 50,51. Ports 52,53 in chamber 45 communicate with sections50,51, respectively. Dip tubes 54,55 connected to sections 50,51,respectively, through end 47 of chamber 45 complete another embodimentof the invention. Of course, in accordance with the invention, dip tubes54,55 will have distinctly different lengths. Thus, if tube 54 is longerthan tube 55, liquid CO₂ introduced through port 52 will flow into thecylinder while CO₂ vapor will rise through tube 55 and exit through port53. A valve will be connected to each of ports 52,53 for flow control.

FIG. 4 shows that, fundamentally, the invention requires only a threadedplug 56 which can be screwed into the sole female-threaded opening atthe top of a CO₂ cylinder, and two tubes 57,58 extending through plug56, one tube 57 reaching close to the bottom of the cylinder and theother tube 58 reaching down only a minor fraction, say about one third,of the height of the cylinder, as illustrated in FIG. 2. Of course, theexterior ends of tubes 57,58 would be connected to the usualaccessories, such as those shown in FIG. 2, to facilitate the flow ofliquid CO₂ down through tube 57 into the cylinder and the flow of CO₂vapor up through tube 58 and out of the cylinder. A third tube may beincluded in plug 56 to serve as an alternate draw-off tube for gaseousCO₂ in the event that liquid CO₂ in tube 58 upon expanding through aregulator (not shown) on tube 58 became clogged with dry ice. Such athird tube would not need to extend below the threaded end of plug 56.In lieu of the third tube, it may be preferable to interpose a streettee (like tee 18 of FIG. 1 without dip tube 19) between the top openingof the CO₂ cylinder and plug 56 as shown in FIG. 4. Thus, the lateralopening of the tee would serve, like a third tube, for the withdrawal ofgaseous CO₂ free of liquid.

To summarize, each of the different structural forms of the apparatus ofthe invention illustrated in FIGS. 1 to 4 provides means for sealing thetop opening of a CO₂ cylinder and two flow passageways extendingtherethrough into the cylinder to different levels therein.

Those skilled in the art will visualize variations and modifications ofthe invention as hereinbefore illustrated without departing from thespirit of scope of the invention. For example, the conventional CO₂cylinder valve can be replaced in FIG. 1 by an elbow with a dip tubeconnected to the end of the elbow which is screwed into the street tee.In any of the embodiments of the invention, the external portion of thetube used for venting CO₂ may be provided with an electric heater toeliminate any plug of dry ice that might form therein. Such a heater onthe external portion of tube 58 in FIG. 4 is a practical substitute forthe optional third tube discussed in relation to FIG. 4. Accordingly,only such limitations should be imposed on the invention as are setforth in the appended claims.

What is claimed is:
 1. An apparatus for introducing liquid CO₂ into ahigh-pressure cylinder having a single top opening and simultaneouslyventing gaseous CO₂ from said cylinder, which comprises sealing meansfor said top opening, and two flow passageways extending through saidsealing means into said cylinder to different levels therein, thepassageway extending to a lower level in said cylinder serving for theintroduction of liquid CO₂ and the passageway extending to a higherlevel in said cylinder serving for the venting of gaseous CO₂ from saidcylinder.
 2. The apparatus of claim 1 wherein the sealing means is achamber with two compartments, and each flow passageway has a port intoone of said compartments and a dip tube extending down from saidcompartment into the cylinder.
 3. In a high-pressure CO₂ cylinder havinga top threaded opening, the improvement of means for introducing liquidCO₂ into, and simultaneously venting gaseous CO₂ from, said cylinder,which comprises a two-compartment chamber installed in said top opening,a first dip tube for introducing liquid CO₂ connected to one compartmentand extending into the bottom portion of said cylinder, a second diptube for venting gaseous CO₂ connected to the other compartment andextending into the upper portion of said cylinder, and a port to eachcompartment outside said cylinder.
 4. The improvement of claim 3 whereinthe two-compartment chamber is formed by a conventional CO₂ valvescrewed to one end of a street tee to provide a first compartment abovea second compartment provided by said tee, the other end of said teebeing installed in the top opening of the CO₂ cylinder, the first diptube is connected to said first compartment, the second dip tube isconnected to said second compartment, the lateral opening of said CO₂valve is the port to said first compartment, and the lateral opening ofsaid tee is the port to said second compartment.
 5. The method offilling the improved CO₂ cylinder of claim 3 with liquid CO₂ whileventing gaseous CO₂ therefrom, which comprises introducing liquid CO₂into the compartment with the connected first dip tube, while ventinggaseous CO₂ from the compartment with the connected second dip tube, andstopping the introduction of liquid CO₂ when the vented CO₂ includesliquid and/or solid CO₂.
 6. The method of filling the improved CO₂cylinder of claim 4 with liquid CO₂ while venting gaseous CO₂ therefrom,which comprises introducing liquid CO₂ into the CO₂ valve while ventinggaseous CO₂ through the lateral opening of the tee, and stopping theintroduction of liquid CO₂ when the vented CO₂ includes liquid and/orsolid CO₂.
 7. An apparatus for filling a high-pressure cylinder having atop threaded opening with liquid CO₂ and simultaneously venting gaseousCO₂ from said cylinder, which comprisesa street tee with first andsecond end ports and a lateral port having said first end port screwedinto said top opening, a first dip tube connected to said first end portand extending into the upper portion of said cylinder, a conventionalCO₂ valve with a lateral port and a bottom hole, a second dip tubeconnected to said bottom hole, said second tube being smaller indiameter to fit loosely in said first tube, said CO₂ valve with saidsecond tube being screwed into said second end port of said tee so thatsaid second tube extends through said tee and said first tube into thebottom portion of said cylinder, said lateral port of said CO₂ valveserving as inlet for liquid CO₂ and said lateral port of said teeserving as outlet for gaseous CO₂.
 8. The method of introducing liquidCO₂ into a high-pressure cylinder equipped with the apparatus of claim 7and simultaneously venting gaseous CO₂ from said cylinder, whichcomprises introducing liquid CO₂ into the lateral port of the CO₂ valve,venting gaseous CO₂ through the lateral port of the street tee, andterminating the introduction of liquid CO₂ when the vented CO₂ is liquidand/or solid.
 9. The method of filling a high-pressure cylinder having atop opening with liquid CO₂ while venting gaseous CO₂ therefrom, whichcomprises installing in said top opening a sealing device having twoflow passageways extending therethrough to different levels in saidcylinder, introducing liquid CO₂ into the passageway that extends to alow level in said cylinder, venting gaseous CO₂ through the passagewaythat extends to a higher level in said cylinder, and stopping theintroduction of liquid CO₂ when the vented CO₂ becomes liquid and/orsolid.
 10. The method of claim 9 wherein the sealing device is a chamberhaving a first compartment with a port and a first dip tube extending toa low level in said cylinder for the introduction of liquid CO₂ and asecond compartment with a port and a second dip tube extending to ahigher level in said cylinder for the venting of gaseous CO₂.
 11. Themethod of claim 10 wherein the first compartment is a conventional CO₂valve and the second compartment is a street tee.